Catheter-related blood stream infection (CR-BSI) in patients with pulmonary hypertension (PH) receiving intravenous iloprost via an indwelling central line has previously not been fully described. Recent studies have suggested a link between the pH of prostanoid infusions and the rate and nature of CR-BSI. We have investigated CR-BSI in patients receiving intravenous iloprost at our unit. Databases and hospital records were interrogated for all patients receiving intravenous iloprost between September 2007 and June 2012. Fifty-nine patients received intravenous iloprost via an indwelling central catheter with a total of 23,072 treatment days. There were 15 episodes of CR-BSI, identified using a systematic screening protocol, involving 11 patients giving an overall CR-BSI rate of 0.65/1,000 treatment days. CR-BSI rate for Gram-positive organisms was 0.26/1,000 treatment-days and for Gram-negative organisms was 0.39/1,000 treatment-days. The pH of iloprost in typical dosing regimens was comparable to the pH used in standard-diluent treprostinil and dissimilar to alkaline epoprostenol infusions. The proportion of Gram-negative CR-BSI was similar to that reported for standard-diluent treprostinil. CRP was normal on admission in 33 % of cases of confirmed CR-BSI and remained normal in 13 % of cases. CR-BSI rates with intravenous iloprost are comparable to those observed for other prostanoids. The high proportion of Gram-negative organisms observed and the neutral pH of iloprost infusions support the previously hypothesised link between pH and antimicrobial activity. Although usually elevated during a CR-BSI, CRP may be normal in early infection and a normal result cannot completely exclude infection.